A simply supported wood beam of rectangular cross section and span length 1.2m carries a concentrated load

Question:

A simply supported wood beam of rectangular cross section and span length 1.2m carries a concentrated load P at mid span in addition to its own weight (see figure). The cross section has width 140mm and height 240mm. The weight density of the wood is 5.4kN/m3.
Calculate the maximum permissible value of the load P if (a) the allowable bending stress is 8.5MPa, and (b) the allowable shear stress is 0.8 MPa.